Method of preparing lubricating



Patented Apr. 25, 1939 STATES METHOD OF PREgiRING- LUBRICATING Gary R.Wagner, Chicago, and Warren A. Raine,

Evanston, Ill., assignors to The Pure Oil Company, Chicago, 111., acorporation of Ohio No Drawing. Application July Serial No. 29,372

13 Claims.

This invention relates to lubricating oils andto the method of preparingthe same. More particularly, the invention is concerned-with a methodfor converting high viscosity oils into oils of lower viscosity and isparticularly applicable to the treatment of so-called Pennsylvaniaparafiin base oils.

The development or high powered and high speed automotive engines hasnecessitated the use of less viscous lubricating oils. The reason forthis is two-fold. First, becauseof the smaller clearances between movingparts and larger surfaces in contact with each other, the friction dragis so great that with viscous oils, the motor cannot be started in coldweather unless more powerful starting equipment is used. Second, thefriction loss is so great when using viscous oils that overheating ofthe motor occurs and fuel consumption is exorbitant.

Not only do the less viscous oils provide easier starting but they alsoprovide superior lubrication. The limit to which the viscosity may bedecreased will be determined by the ability of the oil to form anon-rupturable film under the-loads to which it is subjected. Generallyspeaking, it may be said that the less viscous the oil, the better thelubricating qualities thereof, provided the oil has suificient filmstrength under operating .conditions not to rupture.

As a ,result of the increased demand for low viscosity lubricants, thesupply of-high grade oils is reaching the point where it is becominginsufficient to meet demands whereas the more viscous fractions arebecoming less and less marketable.

One of the objects of the invention is to convert viscous lubricatingoils into less viscous oils.

Another object of the invention is to increase the yield of desiredlubricating fractions from crude mineral oils.

A further object of the invention is to prepare lubricating oils havinga higher viscosity index number than the stock from which it has beenprepared.

Still-another object of the invention is to convert bright stock toneutrals.

Other objects -of the invention will be apparent .from the followingdetailed description.

In accordance with common refining technology, crude oil is subjected todistillation in a shell still to distill off the naphtha, kerosene,

and gas oil. After the removal of the non-viscous fractions thetemperature of the still is gradually raised and steam blown through theoil in increasing amounts to distill off the pressable wax distillate.The temperature is kept below 700 F. and preferably is not permitted toexceed 650 F. By applying a vacuum, lower temperatures may be used.Cracking is avoided as far as possible. In more modern refineries, pipestills are used to distill over the light fractions and the waxdistillate. By the use of eflicient fractionating equipment the variouscuts can be separated in a single distillation. When using pipe stillsit is possible to utilize higher temperatures since the oil is subjectedto the high temperature for a very short period of time. Temperatures upto 750 F., or even 800 F., may be used without causing any substantialcracking of the oil undergoing distillation. Steam and/or vacuum may be"also applied to assist the distillation.

The initial distillation of the crude separates the lubricatingfractions into a less viscous pressable wax distillate and anon-pressable viscous residuum. In some instances a viscous nonpressabledistillate may also be obtained. The residual oil containing theamorphous or nonpressable wax constitutes the cylinder stock. In orderto separate this wax it is necessary to subject the cylinder stock tocold settling or centrifuging. The resulting wax free oil constitutesthe bright stock.

Where the crude is subjected to higher distillation temperatures, as forexample when utilizing pipe still distillation, a deeper cut is madeinto the crude so that a substantial portion distills over to form aviscous non-pressable distillate. This distillate, like the residuum,may be subjected to cold settling or centrifuging to prepare brightstock.

185 seconds (Saybolt Universal) at 100 F., the pressed oil is reduceduntil it attains this viscosity. This is the stock that is generallymarketed for blending with bright stock to furnish different viscosityoils. The amount of such neutrals that may be recovered is approximately35 to 40% of the pressed distillate. Not only must the lubricant meetcertain viscosity specifications but it is essential that it also haveminimum fire and flash tests.

In accordance with the present invention the yield of desirable neutraloil from crude oil can be more than doubled by converting a majorportion of the bright stock into neutrals. This is accomplished bysubjecting bright stock to distillation under light cracking conditionssufficient to reduce the viscosity but not sufiicient to materiallydegrade the lubricating properties thereof. By careful regulation of thedistillation of the bright stock, from 60 to thereof can be taken overas a distillate, leaving a'viscous residuum which is suitable as anindustrial lubricating oil. The overhead distillate, which has arelatively low viscosity compared with the stock from which it isdistilled, is blended with pressed oil distillate and/or otherlubricating oil distillates of low viscosity in proper proportion toproduce a product which, upon reduction of the blend to'desiredviscosity, has the desired flash and fire tests.

If an attempt is made to reduce the distillate from the bright stock tothe: desired viscosity without first blending it with pressed oil orother lubricating oil distillate, the fire and flashtests are too low tomeet required specifications. By blending before distillation, not onlycan a product of satisfactory flash and fire be obtained but the yieldof the desired product is materially increased. If the yields of oil ofdefinite viscosity are obtained by distilling the bright. stockdistillate and the pressed oil separately and these yields compared withthe yield obtained by reducing the blend, it will be found that theyield of oil of the determined viscosity will be in excess of based onthe amount of bright stock used, assuming that the yield of oil frompressed oil will be the same as that obtained when the pressed oil isdistilled separately.

The process may be carried out by first separating crude oil intopressable wax distillate and cylinder stock. This may be done in a shellstill with the aid of steam and/or vacuum or in'a pipe still in themanner previously disclosed. The cylinder stock, whether it be aresiduum or a distillate, is subjected to cold settling or preferablycentrifuging in order to remove the non-pressable wax which is containedtherein and then chemically treated, filtered, and reduced if necessary.The resulting bright stock is subjectedto distillation in either a shellor pipe still in such manner as to lightly crack the stock in order toreduce the viscosity thereof. The distillation step must be carefullycontrolled in order to get a distillate of the desired characteristics.When distilling in a. shell still it is desirable to add a small amount,approximately 10%, of light distillate such as naphtha, kerosene, gasoil or light lubricating oil cuts, to the bright stock in order to startthe distillation without obtaining an excessive amount of cracking. Thetemperature of the still may be gradually raised to approximately 300 F.whereupon steam is introduced in gradually increasing quantities as thedistillation'pro ceeds. The rate of distillation is controlled so thatthe. viscosity of the overhead stream coming 1 from the residue.

off the still ranges between approximately 90 and seconds (SayboltUniversal) viscosity at 100 F. If the resulting distillate is to be usedin the preparation of 180 neutral, that is, lubricating oil distillatehaving a viscosity of 180 seconds S. U. at 100 F., it is preferable tokeep the viscosity of the stream at approximately 100 seconds viscosity.The distillation may be continued until the temperature of the stillreaches approximately 700 F. but preferably should not exceed 650 F. Ifthe distillation is properly carried out approximately 60 to 90% of thecharge may be distilled off, leaving a residue of high flash andviscosity which'is suitable as a lubricating oil for industrial use.

The distillation operation is carried out with a view chiefly toreducing the viscosity of the heavy fractions of the bright stock and atthe same time maintain a high flash and fire test. If the distillationis properly carried out only a small quantity of light crackeddistillate unsuitable as lubricating oil will be formed.

If it is desired to carry out the cracking distillation of bright stockin a pipe still, the distillation is carried out in such manner that theoverhead stream will have a viscosity of between approximately 90 and120 seconds. The heavier material may be recycled through the pipe stilland the distillation continued in'thismanner until approximately 60 to90% of the charge has been taken overhead. When using pipe stilldistillation higher temperatures may be employed ranging up to 750 or800 F. Steam may be used in the vaporizing drum.to strip light fractionsSteam may be also passed through the pipe still together with the oil'to aid in the distillation thereof. When using higher temperatures inpipe still operation the heating should be sufliclently rapid to preventover-cracking of the bright stock.

The distillate resulting from light cracking of the bright stock is thenblended with pressed oil and/or other light lubricating distillate inproportions suitable. to' obtain, upon reduction, a resulting oilof thedesired viscosity, flash and fire tests. The proportions to be blendedwill depend on the characteristics of the resulting products desired aswell as the characteristics of the materials blended and can bedetermined from experience. In the preparation of 180 neutral it hasbeen found that a blend of approximately 70% pressed oil and 30% ofdistillate resulting from the bright stock distillation, will produce aproduct having the required flash'and fire point and viscosity.

Although the invention is applicable to the preparation of neutrals fromPennsylvania, Mid Continent, Gulf Coast, and California oils, it isparticularly suitable inthe preparation of neutrals from Pennsylvania orparaffin baseoils; As an example of the process, as carried out inaccordance with our invention, bright stock from Pennsylvania crude,having the following characteristics, was subjected to a light crackingdistillation. J

Tsar: I

Pennsylvania bright stock Gravity A. P. 1-. 26/27 Flash point, F 530/540Fire point, "F 600/610 Vis. at 210*F.. .r /140 Vis. at 130 F-- --h750/775 Pour point, F. 10/15 Color, A. s. 'r M 6/7 TABLE II DistillateResiduum Bright stock charged, 442 bbls.- Yield, bbls 368 69 Yield,percent 83. 3 15. 6 Gravity, A. P. 32. 4 21. 3 Flash point "1 155 620Fire point, 220 695 Vis. at 100 F., S. U 108 Vis. at 210 F., S. U 258Pour point, F 30 20 Color, A. S. T. M Brown The distillate obtained fromthe distillation of the bright stock was blended with pressed o'ilhaving the following characteristics:

TABLE III Characteristics of pressed oil Gravity, A. P. I 36.6 Flashpoint, F 215 Fire point, F 280 Vis. at 100 F., S. U 61 The blend wasthen subjected to careful distillation with steam in order to preventcracking and to reduce the blend to a 180 seconds viscosity. The resultsof the distillation were as follows:

In another run 222 barrels of bright stock were blended withapproximately of naphtha and the blend subjected to a light crackingdistillation in a shell still in the manner previously set forth. Theresults of the distillation were as follows:

TABLE V Distillate Residuum Bright stock charged, 222 bbls.- Yield, bbls197 32 Yield percent 88. 7 14. 4 omvi A 32. 2 21.3 Flash point, F 110630 Fire point, F.... 160 700 Vis. at 100 F 103 Vis. at 210 254 Yourpoint, F 30 20 Color, A. S. T. M 4+ Brown The distillate prepared fromthis bright stock was blended with pressed oil and "85 stock. The lattermaterial is a distillate which results in the reduction of pressed oilto 180 neutral-and is used to prepare light lubricants havingapproximately 85 seconds viscosity. This stock had the followingcharacteristics:

TABLE VI Characteristics of "85" stock Gravity, A. P. I 35.9 Flashpoint, F 305 Fire point, "F 330 Vis. at 100 F., S.,U 57

The blend was then distilled carefully with steam in order to avoidcracking and the temperature was not permitted to rise in excess of 600F. The results of the distillation were as follows:

TABLE VII Total charge, bbls 429 Pressed oil in charge, bbls 233 Brightstock distillate in charge, bbls 96 "85 stock in charge, bbls 100 Yieldof 180 neutral, bbls; 204 Gravity, A. P. I 31. 3 Flash point, F 420 Firepoint, "F 460- Vis. at 100 F 187' Pour point, F 35 Color, A. S. T. M 5+In order to determine the yield of the 180 neutral from the bright stockdistillate, the variousoils which were blended were separately distilledin order to determine the amount. of 180 neutral that could beobtainedfrom each fraction individually. The fractions were distilled down to180 viscosity bottoms and also were distilled to 420 F. flash pointbottoms. The results were as follows:

TABLE VIII Bright stock Pressed "85 distillate oil stock Percent of 180vis. bottoms 86 36. 5 7 Flash point F. of 180 Vis. bottoms. 375 440 440Percent of 420 F. flash point bottoms 80 40 10 Vis. of 420 F. flashpoint bottoms. 249 165 139 If in Table IV the yield of 180 neutral fromthe pressed oil is assumed to be 36.5% as determined according to TableVIII, the yield of 180 neutral from the bright stock distillate will beover 116%. This unusual result may be accounted for by the fact that aportion of the pressed distillate which is ordinarily too light for 180neutral replaces lighter fractions such as kerosene, naphtha, and gasoil in the bright stock distillate and as a result the yield of neutralsfrom the pressed oil is actually greater than is obtained by straightdistillation of pressed oil.

Likewise, if we assume that the 85 stock will yield 7% of 180 neutraland the pressed oil will yield 36.5%, the yield of 180 neutral from theblend shown in Table VII, based on the bright stock distillate, will beover 117%. On this basis the yield of 180 neutral attributable to thebright stock distillate, will beapproximately 100% based on the brightstock from which the bright stock distillate was prepared.

Although the invention has been described in connection with thepreparation of 180 neutral, it will be understood that the invention isapplicable to the preparation of lubricating oils of other viscosities.This material was selected since it is the stock that is generallymarketed for the purpose of blending with bright stock to prepare thestandard oils that are distributed to the public for use in automotiveengines. The Pennsylvania Grade Crude Oil Association specificationsrequire that the viscosity of the neutrals beat least 180 seconds at100. F. Saybolt Universal and that the flash point be not less than 420F. The blend of bright stock distillate,

pressed oil, and 85 stock given above were selected in order to prepareneutrals meeting these specifications.

One of the unusual results of the invention is that the viscosity indexof the resulting 180 neutral is in excess of the viscosity index ofbright stock; pressed oil, or 85 stock used in the preparation thereof.For example, a product produced by blending 70% of pressed oil and 30%of bright stock distillate prepared in accordance with this invention,had a viscosity index (Dean 8: Davis) of 112, and .a product prepared byblending 92.5% of 85 stock with 7.5% of bright stock distillate, had aviscosity index 'of 108,.whereas the bright stock originally used had aviscosity index of approximately 99, the pressed oil had a viscosityindex of approximately 105, and the "85 stock had a viscosity index of100 to 105.

If the pour point of the bright stock used in preparing the neutrals issufliciently low, the pour point of the neutral prepared by distillingthe blend will be sufficiently 'low to meet commercial requirements. Forexample, if bright stock having a pour point of 10 F. is used, theresulting neutral will have a pour point of approximately 25 F. In theproducts that have been prepared in accordance with this process it hasbeen found that the pour point oi the finished neutral is approximately15 F. above the pour point of the bright stock used in the preparationthereof when prepared from a blend of approximately 30% bright stockdistillate and 70% pressed oil distillate. "Ihe pour point will becorrespondingly lower when smaller proportions of bright stockdistillate are used. The characteristics of the neutrals prepared inaccordance with this invention are in every respect at least equal toneutrals prepared from straight pressed oil distillate and in somerespects are superior thereto.

It will be evident that-it not necessary to use bright stock and pressedoil or other distillate from the same crude for blending. It istherefore possible for a refinery to utilize the entire slocks of brightstock and pressed oilfor the preparation of neutrals since if an excessof -bright stock accumulates it .can be treated in accordance with theprocess andblended with pressed oil which can be purchased, whereas ifan excess of pressed oil accumulates bright stock can be purchasedcheaply and converted into more valuable neutrals.

The residuum remaining from the distillation of the bright stock is aheavy lubricating oil of poor color. By filtering through clay the colorof the residuum may be improved so that it has a dark green fluorescenceand the product is valuable as an industrial oil because of its highflash and fire tests. If a high quality of lubricant is not required,the oil may be used without filtration.

Itwill be evident from the foregoing that the process above described isvaluable for converting less valuable viscous oils into valuable anddesir- 4 able lighter lubricating oils.

What is claimed is: v 1. The method of increasing the yield of neutraloil from wax-bearing crude mineral oils which comprises distilling theoil to separate it into a pressable wax'distillatefraction and cylinderstock, removing the wax from each fraction, subjecting the dewaxedcylinder stock to a'light cracking distillation until the major portionthereof is distilled over, blending the distillate from the lastmentioned distillation with the pressed wax distillate, and reducing theblend to desired viscosity.

2.'The method of preparing lubricating oil which comprises subjectingdewaxed residuum, from which pressable wax distillate has beenseparated, to a light cracking distillation until the major portion ofsaid dewaxed residuum is distilled over,. blending distillate from saiddistillation with dewaxed wax distillate and reducing the blend to thedesired viscosity.

3. Method according to claim 2 in which from 60 to 90% of the dewaxedresiduum is distilled ofl.

4. Method according to claim 2 in which the stream of distillate ismaintained at a viscosity of about 90 to 120 seconds Saybolt Universalat 100 F. during the distillation of the dewaxed re-- A siduum.

5. The method of preparing lubricating oil which comprises subjectingbright stock to a light cracking distillation, maintaining thedistillate stream at a viscosity of approximately 90 to 120 secondsSaybolt Universal at 100 F. during said distillation, dislillingoverhead approximately 60 to 90% of the charge,,blending a minor portionof the distillate with dewaxed distillate, and reduc ing the blend tothe desired viscosity.

6. The method of preparing lubricating oil which comprises blending. aminor portion of a dis.illate, resulting from the light cracking ofbright stock under such conditions that the distillate stream ismaintained ataviscosity of 90 to 120 seconds Saybolt Universal at 100F., with a major portion of pressed wax distillate, and reducing theblend to the desired viscosity.

7. The method of preparing neutral oil having a viscosity approximately180 seconds Saybolt Universal at 100 F. which comprises blendingapproximately 30% of a distillate, resulting from the light cracking ofbright stock under such conditions that the distillate stream ismaintained at approximately 100 seconds Saybolt Universal at 100 F.during the cracking and distilling opera tion, with approximately 70% ofpressed-wax distillate, and reducing the blend until the residuumattains the desired viscosity.

8. The method of preparing lubricating oil from paraflin base crudewhich comprises subjecting the crude oil to non-cracking distillation.

in order to distill. ofi'the pressable wax distillate, dewaxing theresiduum and the wax distillate, subjecting the dewaxed residuum tolight cracking distillation to obtain a further quantity of distillate,blending said last-mentioned distillate with said dewaxed waxdistillates, and reducing the blended distillates to the desiredviscosity.

9. Method in accordance with claim 8 in which a major portion of theresiduum is distilled off during the light cracking distillation.

10. Method in accordance with claim 8 in which a minor portion ofdistillate-from light cracking of residuum is blended with a majorportion of dewaxed wax distillate.

'11. Method in accordance with claim 8/ in which the light crackingdistillation of residuum is carried out in the presence of steam and amajor portion of the residuum is distilled off.

12. Method in accordance with claim 8 in which the residuum ismixed witha light hydrocarbon onds Saybolt Universal at 100 F. until the majorportion or the bright stock distllls over, blending the distillate witha major portion of dewaxed wax distillate, and. reducing the blend tothe desired viscosity, flash, and fire tests.

CAR-Y R. WAGNER.

A. RAIN'E;

